Studies have shown that the number of motor vehicle accidents can be substantially lowered if vehicles have their head lights and park lights illuminated whenever the vehicles are operated, regardless of the time of day or night. There are some requirements that head lights be on at all times that the vehicle is in operation, day and night, on selected road segments. Such tests may lead to the implementation of a requirement that at least head lights be activated when the vehicle is operating at all times.
The ability to automatically illuminate park lights and head lights on a vehicle whenever an engine-driven alternator provides electrical energy to them, regardless of the settings for various light switches, is a very desirable feature for safety reasons. It is also desirable to be able to illuminate automatically one or more display signs that may be associated with the vehicle. With such a feature, the owner of a vehicle may be assured that its lights are on, regardless of whether the operator of the vehicle has remembered to activate a light switch.
At this time, there are two known methods of operating an automatic vehicle illumination system. Following manual methods, the driver of a vehicle turns on his head lights with a manufacturer-supplied switch. This manual operation has to be performed each time the driver enters and leaves the vehicle. Alternatively, known automatic systems which operate without the driver's help become activated every time the vehicle is used, but such systems tend to be complex and expensive to install.
A system of this general type is described and illustrated in Mitchell U.S. Pat. No. 3,832,597. Mitchell discloses a supplementary light energizing means for compelling all of the running lights to be energized, with the exception of high beam headlights, day or night, whenever the ignition switch is placed in a running position and the transmission is set for forward drive.
However, certain disadvantages are implicit in the light control system of the Mitchell patent. First, there is a requirement that the transmission be set for forward drive. This may be inconvenient when the vehicle is stationary with its transmission set in a "park" position with the engine running. Particularly when the vehicle is parked along a thoroughfare, a vehicle owner should still be assured that its lights are on for safety reasons, regardless of whether the operator remembered to turn them on. Second, there is a need to have park lights illuminated, together with any lighted signs that may be associated with the vehicle, as well as head lights. Third, automatic illumination does not occur when the transmission is in "reverse." Therefore Mitchell's approach fails to provide safety when the vehicle is operating in a reverse direction because Mitchell's invention only addresses head lights, not park lights, at the front of the vehicle. Fourth, Mitchell's approach provides no protection in low voltage conditions where an alternator is off-line. In that condition, limited battery power is used to dissipate electrical energy through an unwanted automatic selection of head light illumination.
Consequently, a need exists for improvements in automatic vehicle illumination circuits of this general type which will result in greater reliability and safety.
It would be desirable to have a supplemental system of light control which, when combined with existing vehicle electrical systems, will necessarily ensure an active condition of head lights and park lights whenever the engine is running, regardless of whether the vehicle is in motion or whether the vehicle is being operated in reverse.
With an arrangement of this kind, there should no longer be any need to remember to extinguish the lights after the ignition is turned off, thereby avoiding unwanted battery drainage when manual extinction of the lights is overlooked.
It would also be desirable to have available a passive lighting safety and advertising illumination device which is unaffected by the vehicle operator. No longer would the operator need to remember to activate the lights or, even worse, turn them off when leaving the vehicle.